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Recovery and study of the properties of the sand obtained from the fines from recycled concrete

Hugo KELLERRecovery and study of the properties of the sand obtained from the fines from recycled concrete,Ecole polytechnique de Bruxelles2020 (February).

Concrete is used worldwide and its production needs tremendous amounts of sand. The
recycling of end-of-life concrete becomes more and more interesting economically and
environmentally. Application for particles larger than 4 mm are already existing, however,
the fine fraction below 4 mm caused some issues, namely the separation of the hardened
cement paste glued on others particles. In this report is investigated how different
treatments influence the properties of this fraction. Thus this report presents the
characterization of mortars made from CEM I were the sand has been replaced by the
product of different treatment. Coming from a batch where the size distribution the recycled
concrete was first sieved (with sieve openings of : 4mm, 2mm, 1mm, 0.5mm, 0.212mm,
0.125mm, 0.063mm) before being dehydrated at 550°C. or 750°C, then some of the material
was softly milled in planetary ball mill in order to break hardened cement paste. To look at
the impact of temperature and milling, XRD and XRF and sieving analysis were carried out.
XRD pointed out different changes in microstructure depending of the temperature of
treatment. XRF and PSD analysis showed how the different milling parameters influenced
size and composition. Finally mortars were casted with dehydrated fines or milled material
as sand replacement to compare with mortar with fresh sand. Compression tests and
resoanalysis showed that after 28 days the sample with dehydrated fines had strength 10%
smaller comparing to the reference, on the other hand the compressive strength of mortars
with milled material was 2.5 times smaller than the reference. Concerning Young’s modulus,
both sets where fresh sand was replaced have a modulus about two times smaller than the
reference. These results give good hopes and many paths to explore so that one day sand
could be replaced by some cheap recycled cement material without great mechanical
properties losses and thus making concrete industry more environmentally sustainable.


    author      = "Hugo KELLER",
    title       = "Recovery and study of the properties of the sand obtained from the fines from recycled concrete",
    institution = "Ecole polytechnique de Bruxelles",
    year        = "2020",
    address     = "",
    month       = "February",
    doi         = "",
    note        = "",